[modifier=] in macro, available bindings?

[speak]

i'd like to be able to use the following modifiers in macros:

control-alt
control-shift
shift-alt

but cant find the proper syntax for having 2 key modifiers to run an action.

also, when i use
[modifier=ctrl] /cast spell1
i must hold control and CLICK the button the macro is on, instead of holding control and pressing the KEY the button is on. shift, alt and nomodifier work fine - i can just hold the modifier and press the key the macro is on and the proper spell fires. i use Bongos bar mod if that makes a difference.

Thanks for any help!